A cable television (CATV) system may provide media content, such as video, data, voice, or high-speed Internet services, for example, to subscribers. The cable television system may deliver the media content from a headend to subscriber's client devices over an existing cable television network. The cable television network can take the form of an all-coax, all-fiber, or hybrid fiber/coax (HFC) network.
To keep pace with increasing customer demands for media content and the corresponding explosion in demands for bandwidth, cable television (CATV) systems are seeking solutions for increasing the bandwidth available for upstream and downstream communications. Proposals include extending the upper boundary of the return band frequency by extending the split between the return band and the forward band to allocate more bandwidth to the upstream channel. However, reallocating spectrum to the upstream path means consuming a portion of the spectrum currently dedicated to the downstream path. Increasing the upper boundary of the return band frequency may interfere with CATV components that require transmitting downstream communication signals in the downstream path that fall within the frequency reallocated to the return band.
Further, the cable industry is contemplating adding bidirectional high-speed data services to cable networks to supplement/upgrade existing DOCSIS systems. Such networks may implement Ethernet over coax aiming to offer 1 gigabit per second (Gbps) bidirectional data capacity. However, current solutions require transmission powers that are very high, are problematic to achieve for home-based modems, and/or are costly to support in an amplifier chain.
Proposals to migrate to an advanced DOCSIS system that add bidirectional high speed data services, while retaining existing DOCSIS and video services, require the use of unused spectrum. However, the usable frequency spectrum on cable is limited due to suckouts (e.g., narrow frequency notches with high attenuation) caused by splitters/combiners/amplifier housings and plant maintenance issues. To make use of the limited amount of spectrum, an increased number of bps/Hz in the occupied bandwidth has been proposed to support a 1 Gbps bidirectional data capacity. However, adequate signal to noise ratios are difficult to achieve at high frequencies where cable losses are high.